When we see records being broken and unprecedented events such as this, the onus is on those who deny any connection to climate change to prove their case. Global warming has fundamentally altered the background conditions that give rise to all weather. In the strictest sense, all weather is now connected to climate change. Kevin Trenberth

HIT THE PAGE DOWN KEY TO SEE THE POSTS
Now at 8,800+ articles. HIT THE PAGE DOWN KEY TO SEE THE POSTS

Tuesday, January 31, 2012

“If you’re younger than 26, you have never seen a month where the global mean was as cold as the 161 year average,” observes Robert Grumbine. In contrast, “there are no periods as long as even 20 years of continual below reference temperatures.” He finds that the period 1880-1940 seems to best represent a stable long-term average for global temperatures. If that’s the case, then the “last time the global mean was below the climate normal was March, 1976. If you’re 35 or younger, you have never seen a global mean below climate’s real normal.”

Monday, January 30, 2012

The rate of Arctic climate change was now faster than ecosystems and traditional Arctic societies could adapt to.

The Sydney Morning Herald, January 31, 2012

WA-based scientists have warned of "dire consequences" to the human race after detecting the first signs of dangerous climate change in the Arctic.

The scientists, from the University of WA, claim the region is fast approaching a series of imminent "tipping points" which could trigger a domino effect of large-scale climate change across the entire planet.

In a paper published in the Royal Swedish Academy of Sciences' journal AMBIO and Nature Climate Change, the lead author and director of UWA's Oceans Institute, Winthrop Professor Carlos Duarte, said the Arctic region contained arguably the greatest concentration of potential tipping elements for global climate change

"If set in motion, they can generate profound climate change which places the Arctic not at the periphery but at the core of the Earth system," Professor Duarte said. "There is evidence that these forces are starting to be set in motion."

"This has major consequences for the future of human kind as climate change progresses."

Professor Duarte said the loss of Arctic summer sea ice forecast over the next four decades − if not before − was expected to have abrupt knock-on effects in northern mid-latitudes, including Beijing, Tokyo, London, Moscow, Berlin and New York.

Research showed that the Arctic was warming at three times the global average and the loss of sea ice – which had melted faster in summer than predicted − was linked tentatively to recent extreme cold winters in Europe.

Professor Duarte − winner of last year's prestigious Prix d'Excellence awarded by the International Council for the Exploration of the Sea − said the most dangerous aspect of Arctic climate change was the risk of passing critical "tipping points."

In the next 10 years, Professor Duarte warned summer sea ice could be largely confined to north of coastal Greenland and Ellesmere Island, and was likely to disappear entirely by mid-century.

A drop in Arctic ice had opened new shipping routes, expanded oil, gas and mineral exploitation and led to new harbours, houses, roads, airports, power stations and other support facilities.

It had triggered a new gold rush to access these resources, with recent struggles by China, Brazil and India to join the Arctic Council where the split of these resources was being discussed.

But increased deposits of black carbon (soot) from coal-burning power stations had accelerated warming and ice melt.

Professor Duarte said the rate of Arctic climate change was now faster than ecosystems and traditional Arctic societies could adapt to.

The Arctic was expected to stop being a carbon dioxide sink and become a source of greenhouse gases if seawater temperatures rose by 4-5C.

"It represents a test of our capacity as scientists, and as societies to respond to abrupt climate change," Professor Duarte said.

"We need to stop debating the existence of tipping points in the Arctic and start managing the reality of dangerous climate change.

"We argue that tipping points do not have to be points of no return.

"Several tipping points, such as the loss of summer sea ice, may be reversible in principle − although hard in practice.

"However, should these changes involve extinction of key species − such as polar bears, walruses, ice-dependent seals and more than 1000 species of ice algae − the changes could represent a point of no return.

"Confusion distracts attention from the urgent need to focus on developing early warning indicators of abrupt climate change, address its human causes and rebuild resilience in climate, ecosystems and communities.

Trends and tipping point in the climate system: portents for the 21st century

Andrew Glikson (Earth and Palaeo climate science , Australian National University )

Mass extinctions in the history of Earth occurred when the atmosphere-ocean-land carbon and oxygen cycles, on which the biosphere depends, have been perturbed at rates to which species could not adapt. Rising atmospheric greenhouse gas levels above 330 ppm CO2 at rates of ~2 ppm/year and mean temperature rise of ~0.02 oC/year since 1975 and 1976 are driving the fastest climate change trend recorded since about 34 million years ago, representing a critical climate threshold leading into uncharted territory and threatening the biosphere and human civilization. It is suggested the arrest of carbon emissions may not be sufficient to halt the current trend, except if accompanied with global efforts at drawdown of atmospheric CO2 using a range of bio and sequestration, organic and chemical methods.

The future of human kind faces dire consequences due to arguably the first signs of dangerous climate change in the Arctic, say leading international scientists from The University of Western Australia.

They say the Arctic region is fast approaching a series of imminent "tipping points" that could trigger an abrupt domino effect of large-scale climate change across the entire planet.

In a paper published in the Royal Swedish Academy of Sciences' journal AMBIO and a parallel commentary in Nature Climate Change, the lead author and Director of the University's Oceans Institute, Winthrop Professor Carlos Duarte, said the Arctic region contained arguably the greatest concentration of potential tipping elements for global climate change.

"If set in motion, they can generate profound climate change which places the Arctic not at the periphery but at the core of the Earth system," Professor Duarte said. "There is evidence that these forces are starting to be set in motion."

"This has major consequences for the future of human kind as climate change progresses."

Professor Duarte said the loss of Arctic summer sea ice forecast over the next four decades - if not before - was expected to have abrupt knock-on effects in northern mid-latitudes, including Beijing, Tokyo, London, Moscow, Berlin and New York.

Research showed that the Arctic was warming at three times the global average and the loss of sea ice - which had melted faster in summer than predicted - was linked tentatively to recent extreme cold winters in Europe.

Professor Duarte - winner of last year's prestigious Prix d'Excellence awarded by the International Council for the Exploration of the Sea - said the most dangerous aspect of Arctic climate change was the risk of passing critical "tipping points".

Arctic records showed unambiguously that sea ice volume had declined dramatically over the past two decades, Professor Duarte said. In the next 10 years, summer sea ice could be largely confined to north of coastal Greenland and Ellesmere Island, and was likely to disappear entirely by mid-century.

"Some environmental and biological elements may be linked in a domino effect of tipping points that cascade rapidly once the summer sea ice is lost," Professor Duarte said.

A drop in Arctic ice had opened new shipping routes, expanded oil, gas and mineral exploitation, increased military and research use, and led to new harbours, houses, roads, airports, power stations and other support facilities

It had triggered a new gold rush to access these resources, with recent struggles by China, Brazil and India to join the Arctic Council where the split of these resources was being discussed.

But increased deposits of black carbon (soot) from coal-burning power stations and stoves on snow and ice had accelerated warming and ice melt.

Top predators such as polar bears were declining, more methane gas was entering the atmosphere as permafrosts and submarine methane hydrates thawed, freshwater discharge had increase 30 per cent recent years and the Arctic Sea was warming faster as the ice cap melted, trapping more solar heat instead of reflecting it back into space.

In the subarctic region, dieback of the boreal forest and desiccation of peat deposits leading to uncontrolled peat fires (such as those that affected Russia in the summer of 2010) would further enhance greenhouse gas emissions.

Professor Duarte said the rate of Arctic climate change was now faster than ecosystems and traditional Arctic societies could adapt to.

The Arctic was expected to stop being a carbon dioxide sink and become a source of greenhouse gases if seawater temperatures rose 4-5ºC.

"It represents a test of our capacity as scientists, and as societies to respond to abrupt climate change," Professor Duarte said.

"We need to stop debating the existence of tipping points in the Arctic and start managing the reality of dangerous climate change.

"We argue that tipping points do not have to be points of no return.

"Several tipping points, such as the loss of summer sea ice, may be reversible in principle - although hard in practice.

"However, should these changes involve extinction of key species - such as polar bears, walruses, ice-dependent seals and more than 1000 species of ice algae - the changes could represent a point of no return.

"Confusion distracts attention from the urgent need to focus on developing early warning indicators of abrupt climate change, address its human causes and rebuild resilience in climate, ecosystems and communities."

Estimating the global radiative impact of the sea ice–albedo feedback in the Arctic

Stephen R. Hudson (Norwegian Polar Institute, Tromsø, Norway)

Key points:

The radiative forcing due to sea ice loss can be simply calculated

Current forcing is small, around 0.1 W/m2; it could increase to about 0.3 W/m2

Better understanding of related cloud changes is critical for full understanding

Abstract

A simple method for estimating the global radiative forcing caused by the sea ice–albedo feedback in the Arctic is presented. It is based on observations of cloud cover, sea ice concentration, and top-of-atmosphere broadband albedo. The method does not rely on any sort of climate model, making the assumptions and approximations clearly visible and understandable and allowing them to be easily changed. Results show that the globally and annually averaged radiative forcing caused by the observed loss of sea ice in the Arctic between 1979 and 2007 is approximately 0.1 W m−2; a complete removal of Arctic sea ice results in a forcing of about 0.7 W m−2, while a more realistic ice-free summer scenario (no ice for 1 month and decreased ice at all other times of the year) results in a forcing of about 0.3 W m−2, similar to present-day anthropogenic forcing caused by halocarbons. The potential for changes in cloud cover as a result of the changes in sea ice makes the evaluation of the actual forcing that may be realized quite uncertain since such changes could overwhelm the forcing caused by the sea ice loss itself, if the cloudiness increases in the summertime.

Vast quantities of methane are trapped in oceanic hydrate deposits. Because methane is a powerful greenhouse gas (about 26 times more effective than CO2), there is considerable concern that a rise in the temperature of the oceans will induce dissociation of oceanic hydrate accumulations, potentially releasing large amounts of carbon into the atmosphere. Such a release could have dramatic climatic consequences because it could amplify atmospheric and oceanic warming and possibly accelerate dissociation of the remaining hydrates. This study assesses the stability of three types of hydrates (case I, deep-ocean deposits; case II, shallow, warm deposits; and case III, shallow, cold deposits) and simulates the dynamic behavior of these deposits under the influence of moderate ocean temperature increases. The results indicate that deep-ocean hydrates are stable under the influence of moderate increases in ocean temperature; however, shallow deposits can be very unstable and release significant quantities of methane under the influence of as little as 1 °C of seafloor temperature increase. Less permeable sediments, or burial underneath layers of hydrate-free sediment, affect both the rate of hydrate dissociation and methane transport to the seafloor but may not prevent methane release. Higher-saturation deposits can produce larger methane fluxes with the thermodynamics of hydrate dissociation retarding the rate of recession of the upper hydrate interface. These results suggest possible worst case scenarios for climate-change-induced methane release and point toward the need for detailed assessment of the hydrate hazard and the coupling of hydrate-derived methane to regional and global ecosystems.

Received 30 May 2008; accepted 13 October 2008; published 24 December 2008.

Two years ago, scientists at the National Center for Atmospheric Research in Boulder, Colo., released a study claiming that inconsistencies between satellite observations of Earth's heat and measurements of ocean heating amounted to evidence of "missing energy" in the planet's system.

Where was it going? Or, they wondered, was something wrong with the way researchers tracked energy as it was absorbed from the sun and emitted back into space?

An international team of atmospheric scientists and oceanographers, led by Norman Loeb of NASA's Langley Research Center in Hampton, Va., and including Graeme Stephens of NASA's Jet Propulsion Laboratory in Pasadena, Calif., set out to investigate the mystery.

They used 10 years of data -- spanning 2001 to 2010 -- from NASA Langley's orbiting Clouds and the Earth's Radiant Energy System Experiment (CERES) instruments to measure changes in the net radiation balance at the top of Earth's atmosphere. The CERES data were then combined with estimates of the heat content of Earth's ocean from three independent ocean-sensor sources.

Their analysis, summarized in a NASA-led study published Jan. 22, 2012, in the journal Nature Geosciences, found that the satellite and ocean measurements are, in fact, in broad agreement once observational uncertainties are factored in.

"One of the things we wanted to do was a more rigorous analysis of the uncertainties," Loeb said. "When we did that, we found the conclusion of missing energy in the system isn't really supported by the data."

"Missing Energy" is in the Ocean

"Our data show that Earth has been accumulating heat in the ocean at a rate of half a watt per square meter (10.8 square feet), with no sign of a decline," Loeb said. "This extra energy will eventually find its way back into the atmosphere and increase temperatures on Earth."

Scientists generally agree that 90% of the excess heat associated with increases in greenhouse gas concentrations gets stored in Earth's ocean. If released back into the atmosphere, a half-watt per square meter accumulation of heat could increase global temperatures by 0.3 or more degrees centigrade (0.54 degree Fahrenheit).

Loeb said the findings demonstrate the importance of using multiple measuring systems over time, and illustrate the need for continuous improvement in the way Earth's energy flows are measured.

The science team at the National Center for Atmospheric Research measured inconsistencies from 2004 and 2009 between satellite observations of Earth's heat balance and measurements of the rate of upper ocean heating from temperatures in the upper 700 meters (2,300 feet) of the ocean. They said the inconsistencies were evidence of "missing energy."

Other authors of the paper are from the University of Hawaii, the Pacific Marine Environmental Laboratory in Seattle, the University of Reading United Kingdom and the University of Miami.

An often-used figure in estimates of the size of permafrost stores is 1672 Gt (or Pg, or billion tonnes) of Carbon. This figure relates to organic carbon and refers to terrestrial permafrost stores. (1)

This figure was recently updated to 1700 Gt of carbon, projected to result in emissions of 30 - 63 Gt of Carbon by 2040, reaching 232 - 380 Gt by 2100 and 549 - 865 Gt by 2300. These figures are carbon dioxide equivalents, combining the effect of carbon released both ascarbon dioxide (97.3%) and as methane (2.7%), with almost half the effect likely to be from methane. (2)

In addition to these terrestrial stores, there is methane in the oceans and in sediments below the seafloor. There are methane hydrates and there is methane in the form of free gas. Hydrates contain primarily methane and exist within marine sediments particularly in the continental margins and within relic subsea permafrost of the Arctic margins. (3)

Hunter and Haywood estimate that globally between 4700 and 5030 Pg (Gt) of Carbon is locked up within subsea hydrate within the continental margins. This does not include subsea permafrost-hosted hydrates and so those of the shallow Arctic margin (<~300m) were not considered. (3)

Dallimore and Collett (1995) found high methane concentrations in ice-bonded sediments and gas releases suggest that pore-space hydrate may be found at depths as shallow as 119 m. (4) Recent studies indicate that hydrate formation can occur in upper gas-saturated horizons (up to 100-200 m) of permafrost. (5) Furthermore, methane hydrates have been found in Siberia at depths as shallow as 20 m. (6)Shakhova et al. estimate the accumulated methane potential for the Eastern Siberian Arctic Shelf (ESAS, rectangle on image right) alone as follows:

The East Siberian Arctic Shelf covers about 25% of the Arctic Shelf (3) and additional stores are present in submarine areas elsewhere at high latitudes. Importantly, the hydrate and free gas stores contain virtually 100% methane, as opposed to the organic carbon which the above study (2) estimates will produce emissions in the ratio of 97.3% carbon dioxide and only 2.7% methane when decomposing.

How stable is this methane?

The sensitivity of gas hydrate stability to changes in local pressure-temperature conditions and their existence beneath relatively shallow marine environments mean that submarine hydrates are vulnerable to changes in bottom water conditions (i.e. changes in sea level and bottom water temperatures). Following dissociation of hydrates, sediments can become unconsolidated, and structural failure of the sediment column has the potential to trigger submarine landslides and further breakdown of hydrate. The potential geohazard presented to coastal regions by tsunami is obvious. (3)

Further shrinking of the Arctic ice-cap results in more open water, which not only absorbs more heat, but which also results in more clouds, increasing the potential for storms that can cause damage to the seafloor in coastal areas such as the East Siberian Arctic Shelf (ESAS, rectangle on image left), where the water is on average only 45 m deep. (8)

Much of the methane released from submarine stores is still broken down by bacteria before reaching the atmosphere. Over time, however, depletion of oxygen and trace elements required for bacteria to break down methane will cause more and more methane to rise to the surface unaffected. (9)

There are only a handful of locations in the Arctic where (flask) samples are taken to monitor the methane. Recently, two of these locations showed ominous levels of methane in the atmosphere (images below).

The danger is that large abrupt releases will overwhelm the system, not only causing much of the methane to reach the atmosphere unaffected, but also extending the lifetime of the methane in the atmosphere, due to hydroxyl depletion in the atmosphere.

Shakhova et al. consider release of up to 50 Gt of predicted amount of hydrate storage as highly possible for abrupt release at any time. (10)

What would be the impact of methane releases from hydrates in the Arctic?

If an amount of, say, 1 Gt of methane from hydrates in the Arctic would abruptly enter the atmosphere, what would be the impact?

Methane's global warming potential (GWP) depends on many variables, such as methane's lifetime, which changes with the size of emissions and the location of emissions (hydroxyl depletion already is a big problem in the Arctic atmosphere), the wind, the time of year (when it's winter, there can be little or no sunshine in the Arctic, so there's less greenhouse effect), etc. One of the variables is the indirect effect of large emissions and what's often overlooked is that large emissions will trigger further emissions of methane, thus further extending the lifetime of both the new and the earlier-emitted methane, which can make the methane persist locally for decades.

The IPCC (2007) gives methane a lifetime of 12 years, and a GWP of 25 over 100 years and 72 over 20 years. (11)

The image by Dessus (2008) below illustrates how methane's GWP depends on the horizon over which its impact is calculated. (12)

Drew Shindell (2009) points out that the IPCC figures do not include direct+indirect radiative effects of aerosol responses to methane releases that increase methane's GWP to 105 over 20 years when included. (13)

Using the IPCC figures, applying a GWP of 72 times carbon dioxide would give 1 Gt of methane a greenhouse effect equivalent to 72 Pg of carbon dioxide over 20 years. Applying a GWP of 105 times carbon dioxide would give 1 Gt of methane a greenhouse effect equivalent to 105 Pg of carbon dioxide over 20 years.

Note that this 174 Pg C was released over a period of 150 years, allowing sinks time to absorb part of the burden. Note also that, as emissions continue to rise, some sinks may turn into net emitters, if they haven't already done so.

The image on the left shows the impact of 1 Gt of methane, compared with annual fluxes of carbon dioxide based on the NOAA carbon tracker. (15)

Fossil fuel and fires have been adding an annual flux of just under 10 Pg C since 2000 and a good part of this is still being absorbed by land and ocean sinks.
In other words, the total burden of all carbon dioxide emitted by people since the start of the industrial revolution has been partly mitigated by sinks, since it was released over a long period of time.

Furthermore, the carbon dioxide was emitted (and partly absorbed) all over the globe, whereas methane from such abrupt releases in the Arctic would - at least initially - be concentrated in a relatively small area, and likely cause oxygen depletion in the water and hydroxyl depletion in the atmosphere, extending methane's lifetime, while triggering further releases from hydrates in the Arctic.

This makes it appropriate to expect a high initial impact from an abrupt 1 Gt methane release, i.e. at a GWP of well over 100 times the greenhouse effect of carbon dioxide, which will last for decades.

Even more terrifying is the prospect that this would trigger further methane releases. Given that there already is ~5 Gt in the atmosphere, the impact of this initial 1 Gt combined with further releases of, say, 4 Gt of methane would result in a burden of 10 Gt of methane. When applying a GWP of 105 times carbon dioxide, this would result in a greenhouse effect equivalent to 1050 Pg of carbon dioxide over 20 years.

In conclusion, a release of 1 Gt of methane in the Arctic would be catastrophic and the methane wouldn't go away quickly either, since this would be likely to keep triggering further releases. While some models project rapid decay of the methane, those models often use global decay values and long periods, which is not applicable in case of such abrupt releases in the Arctic.

Instead, the methane is likely to stay active in the Arctic for decades at a very high warming potential, due to depletion of hydroxyl and oxygen, while the resulting summer warming (when the sun doesn't set) is likely to keep triggering further releases in the Arctic.